Vented or Unvented system

[bernardgreen]

Given that an unvented system must be installed by and then for safetey be regularily serviced by a qualified technician what advantages does an unvented system offer over and above a vented system ?

The vented system has the dis-advantage of requiring a cold water supply tank located somewhere higher than the hot water cyclinder. The cold water supply tank however provides a back up store of water for flushing toilets should the mains supply not be available.

 

[Madrab]

No need for a separate cold water cistern - more cost - space requirement.

More importantly - mains pressure hot water!

 

[bernardgreen]

No need for a separate cold water cistern - more cost - space requirement.

But there is a need for an expansion vessel, safety devices and drainage pipe work that will take hot water if the pressure relief valve opens. Whatis the cost comparison of them to a cold water tank ?

More importantly - mains pressure hot water!

Is mains pressure hot water an absolute necessity ? Being drenched by mains pressure cold water can be un-pleasant but is relatively harmless, being drenched with mains pressure hot water is a different matter.

Mains pressure hot water for a shower is possible from a second coil in a vented hot water tank.

 

[middleman]

The main reason for me is mains hot water pressure to the shower in the bathroom and ensuite without any noisy power showers or pumps.

You will find that most countries in Europe have pressurised hot water systems and the UK is one of few who are 50/50. Manufacturers tend to make more taps, showers etc to suit this than gravity fed.

I found that this restricted me somewhat with choices when planning bathrooms.

 

[Madrab]

No need for a separate cold water cistern - more cost - space requirement.

But there is a need for an expansion vessel, safety devices and drainage pipe work that will take hot water if the pressure relief valve opens. Whatis the cost comparison of them to a cold water tank ?

When it comes to attics then I find more and more that they are being used as living/storage space or there are space restrictions making it difficult to provide space for a 50 gal cistern especially in new build designs. A cylinder fed from a cistern in an cupboard gives very poor flow and pressure and invariably needs to be pumped. All the safety components needed for a pressurised system could all be incorporated in one boiler unit at a set cost.

More importantly - mains pressure hot water!

Is mains pressure hot water an absolute necessity ? Being drenched by mains pressure cold water can be un-pleasant but is relatively harmless, being drenched with mains pressure hot water is a different matter.

Everyone seems to be looking for a great powerful shower these days, not surprisingly, so mains hot water seems to be desirable, an un-vented cylinder will provide an adequate amount. Choosing a TMV2/3 mixing valve or thermostat will avoid scalding risks.

Of course there are other alternatives, thermal stores etc but the question was about vented or un-vented

 

[bernardgreen]

Of course there are other alternatives, thermal stores etc but the question was about vented or un-vented

It does seem the only valid reasons for un-vented are lack of space for tanks in the loft and the "need" for high pressure hot water at the shower head.

Maybe I should have expanded the question to consider the use of thermal stores. Then it expands to two options

[1] vented hot water storage cyclinder with the water in the cylinder being the low pressure hot supply to baths, basins and sinks and mains pressure water through a heat exchanger to supply showers.

[2] the water in the store is not used but remains in the store / boiler circuit and all hot water for baths basins sinks and showers passes through the heat exchnage in the store.

My contacts with architects and designers of eco systems leads me to believe that the majority of installers are "tradditional" and do not want to go outside their comfort zone and consider non convential methods for provide the client with the best options.

 

[Dan Robinson]

Most architects and designers of eco systems are half wits.

 

[bernardgreen]

Most architects and designers of eco systems are half wits.

A few may be........

If one is generalising then it could be said that most tradesmen can follow the rule books but it takes an engineer to write the rule books.

Was it a half wit designer who designed your favourite boiler ?